Tension spring supporting arrangement



March 31, 1970 F. F. DOMYAN TENSION SPRING SUPPORTING ARRANGEMENT 2 Sheets-Sheet 1 Filed April 5, 1968 r mm, 3 V F. m R M v 3 m 2 T W m Wm W A S v z g I m & w n E g Q QQQMmwN QSk w m2! QR QQ ubbvwqxm a m sw mm Q Q w m@ M M 6% U- wm mm vm ww MMQQKQY um ubswmfii Nm m NM. QB v N mw March 31, 1910 F. DOMYAN $503,303

TENSION srnme surroawme ARRANGEMENT Filed April 5. 1968 2 Sheets-Sheet z ii. L 56 E I I I ll 11] INVENTOR- F. F DOMW/V A mm United States Patent O 3,503,303 TENSION SPRING SUPPORTING ARRANGEMENT Frank Francis Domyan, North Hollywood, Calif., assignor to International Telephone and Telegraph Corporation, New York, N.Y., a corporation of Delaware Filed Apr. 3, 1968, Ser. No. 718,448 Int. Cl. F15b 9/08, 13/16; F16h 21/44 US. CI. 9147 3 Claims ABSTRACT OF THE DISCLOSURE The invention relates to an improvement in a control employed in a hydraulic apparatus which has a vertical piston rod that controls a large force by the use of a small change in fluid pressure. The small changein fluid pressure is achieved by varying the amount of hydraulic fluid which is permitted to escape from a bleed nozzle by the use of a vane movable toward and away from the nozzle orifice. The improved control employs a vertical feedback spring which is connected through a pivoted arm to the piston rod in such a manner that the spring remains vertical regardless of the vertical position of the rod.

BACKGROUND OF THE INVENTION This invention relates generally to a hydraulic positioning device and, more particularly, to the feed-back control between the piston rod of the device and the mechanism which determines the position of the rod.

In the United States Patent No. 3,087,471 to W. A. Ray, there is disclosed a hydraulic positioning apparatus in which the control mechanism that establishes the position of a piston slidable in a cylinder includes a vane that is operated by electromagnetic means to vary the fluid pressure inside a nozzle. With this apparatus it is possible to control an extremely large force for shifting the piston in the cylinder by controlling the fluid which is bled through the nozzle orifice by the vane. In the Ray apparatus, the control includes an electrical feed-back between the piston and the vane so that the vane will return to an equilibrium position spaced from the nozzle orifice after the electromagnetic control therefor has caused the piston rod to shift to a new position. In a modified form of this hydraulic positioning apparatus, a coil spring is employed in the feed-back mechanism between the piston and the vane. This spring is normally vertically disposed, as is the piston, and is connected to a pivoted arm the position of which is determined by the position of the piston. This control mechanism has the disadvantage that it does not provide linearity in the operation of the apparatus with the result that the apparatus operates somewhat erratically. It is the object of the present invention to overcome this problem.

SUMMARY OF THE INVENTION According to the principal aspect of the present invention, I have discovered that the erratic operation of the aforementioned hydraulic positioning device employing a'feed-back spring in the control mechanism thereof is due to the fact that the spring does not remain vertical during movement of the piston to various vertical positions. In other words, I have found that non-erratic behavior of the apparatus can be achieved by connecting the coil spring to the pivoted arm that is moved by the piston in such a manner that the spring remains vertical regardless of the position of the piston. In the preferred form of the invention, a curved generally vertically extending surface is provided on the pivoted arm. This surface is shaped so as to have a constant radius of curvature, the center of which is coincident with the pivot point of the arm. The spring is connected to the upper portion of ice this surface by a flexible element so that within the normal limits of pivotable movement of the arm, the flexible element bears against the curved surface of the arm. This causes the element to remain in a single vertical plane which is tangential to the curved surface regardless of the position of the arm. Since the flexible element remains in such fixed vertical plane, the feed-back spring connected thereto also remains in a vertical disposition so that there is direct linear relationship between the movement of the piston and that of the feed-back spring.

Other objects, aspects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates in somewhat schematic form the hydraulic positioning apparatus in which the novel control of the present invention is provided;

FIG. 2 is a top plan view of the control;

FIG. 3 is a side elevational view of the control shown in FIG. 2, with the piston rod of the apparatus shown in a relatively low position;

FIG. 4 is a side elevational view of the control showing the piston rod in a relatively high position; and

FIG. 5 is an end elevational view of the pivoted arm and of the feedback spring of the control as viewed from line 55.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to hte drawings in detail, there is illustrated in FIG. 1 a hydraulic positioning apparatus, generally designated 10. The apparatus 10 comprises a hydraulic fluid reservoir 12 connected by a conduit 14 to a hydraulic pump 16. The output of the pump is conveyed through conduits 18 and 20 to a hydraulic actuator, generally designated 22. This actuator includes a piston 24 which is slidable in a vertically extending cylinder 26. A piston rod 28 fixed to the piston 24 extends through the upper and lower ends of the cylinder. A spring 30 biases the piston rod in a downward direction.

Fluid pressure to the cylinder 26 is controlled by a hydraulic amplifier 32 which is identical to that shown in the aforementioned Ray patent. The output of the amplifier is bled through a nozzle 34 via a conduit 36. A lever arm 38 pivotally mounted at 40 intermediate its ends carries a vane 42 which controls the amount of hydraulic fluid which may be bled from the nozzle 34 and thus the pressure inside the nozzle. The arm 38 is actuable by an electromagnetic device 43. This device includes a fixedly mounted ferromagnetic core 44 which changes the position of a coil 46 fixed to the right end of arm 38 depending upon the amount of current which is supplied to the coil. The pivoted arm 38, vane 42 and electromagnetic device 43 constitute means for controlling the pressure at the nozzle 34 and thus the fluid pressure delivered to the cylinder 26, as will be seen later.

A servo balance control, generally designated 48, is provided between the arm 38 and the piston rod 28. This control includes a pair of adjacent arms 50 and 52 which are pivotally mounted at opposite ends at 54 and 56, respectively, for vertical movement in planes parallel to each other. A vertically disposed feed-back spring 58 is connected between the free end of the arm 52 and the left end of the arm 38 so as to oppose the force exerted by the coil 46. The upper end 60 of the piston rod 28 bears against the end 62 of the arm 50. The arm 50 carries an axially adjustable lateral projection 64 which engages the under-side 66 of arm 52.

In operation of the apparatus 10, piston 24 will assume a position in cylinder 26 depending upon the spacing between the vane 42 and nozzle. 34 which is determined by the current flowing in the coil 46. When the apparatus is in an equilibrium condition the vane 42 will be spaced from the nozzle 34 essentially as shown in FIG. 1. If the electromagnetic device 43 is energized to tend to close the nozzle 34 by pivoting the arm 38 in a counterclockwise direction, the fluid pressure within the nozzle 34 will increase. This increase in pressure will be magnified through the amplifier 32 to increase the pressure in conduit and thereby shift the piston 24 upwardly to a new position.

During this transient movement of the piston, the lever arm 50 will be pivoted upwardly due to its engagement with the upper end of the piston rod 28. Upward movement of the arm 50 effects upward movement of the arm 52 via the projection 64, thus tensioning or extending the spring 58. Extending of the spring 58 rotates the arm 38 in a clockwise direction to move the vane 42 away from the nozzle 34 back to its normal equilibrium position whereupon it is spaced from the nozzle as shown. If the current in the coil 46 is decreased, the vane 42 will tend to move away from the nozzle 34, thus reducing the pressure in line 20 and permitting the spring 30 to shift the piston 24 in a downward direction. During this transient movement of the piston, the servo balance control 48 will return the vane 42 to its equilibrium position.

A more detailed showing of the control mechanism for altering the fluid pressure at the nozzle 34 and of the servo balance control 48 is illustrated in FIGS. 2 to 5, wherein the reference numerals utilized in FIG. 1 are employed to designate corresponding elements. As best seen in FIG. 3, the arm 52 includes a first part 70 which is pivotally mounted at 56 and a second part 72 which extends beyond the end 74 of part 7 0 and is fixed to part 70 at 76. As best seen in FIG. 2, the arms 50 and 52 extend generally laterally above the arm 38 with the end 74 of the part 70 disposed above the vertically disposed coil spring 58. A cylindrical balance weight 78 is threaded through the end of arm 38 opposite the electromagnetic device.

As previously stated, I have discovered that non-erratic operation of the apparatus discolsed herein can be achieved by providing an arrangement in which the spring 58 is caused to remain in a vertical position regardless of the vertical position of the piston rod 28. In accordance with the present invention, I have achieved this result by shaping the end 74 of the arm part 70 so as to be curved in a generally vertical direction extending above the spring 58 with the curved surface having a constant radius of curvature the center of which is coincident with the pivot point 56. In addition, the spring 58 is connected to the arm part 70 by means of a relatively flat thin flexible metal strip 80 which is connected at its upper end by means of a screw 82 to an upper portion of the curved surface 74 while the lower end of the strip 80 is folded upwardly upon itself and provided with an aperture 84 through which the upper hooked end 86 of the spring 58 passes.

In the normal operation of the apparatus 10, the piston rod 28 is movable between the lower and upper limits seen in FIGS. 3 and 4, respectively. As a consequence, the pivoted arms 50 and 52 are limited in their movement between the positions shown in these two figures. When these arms are in either of the positions shown in FIGS. 3 and 4, and also in any intermediate position therebetween, the upper end of strip 80 constantly bears against the curved surface 74. As a consequence, the lower free end of the strip remains in a fixed vertical plane which is tangential to the curved surface. Since the lower portion of the strip remains in this fixed vertical plane, the force applied upon the spring 58 through the strip 80 is always in a vertical direction so that the spring will remain in a vertical disposition regardless of the vertical position of the piston rod 28. As a consequence, there is a direct linear relationship between the movement of the piston rod 28 and spring 58 within the limits of pivotable movement of arm 52 with the result that the hydraulic positioning apparatus 10 in which the spring mounting arrangement of the present invention is employed functions in an accurate and nonerratic manner.

I In addition, the relatively wide width of the metal strip 80 with respect to its thickness prevents erratic behavior of the apparatus due to friction and slippage with respect to the curved surface 74, thus improving the operating characteristics of the apparatus 10.

What is claimed is:

1. In a hydraulic positioning device, an axially shiftable, vertically disposed piston rod and control means therefor, said control means including a vertically adjustable member, the position of which determines the vertical position of said rod, a vertically disposed spring above said member, an arm mounted for generally vertical pivotable movement above said spring, means connecting said spring between said arm and said member, and linkage means interconnecting said rod and arm so that upward movement of said rod extends said spring, said connecting means cooperating with said arm in a manner to cause said spring to remain vertically disposed within the limits of pivotable movement of said arm regardless of the vertical position of said rod, said arm having a curved, generally vertically extending, surface above said spring, said surface having a constant radius of curvature, the center of which is coincident with the pivot point of said arm, said connecting means including a flexible element fastened at its lower end to said spring, and means fixing an upper portion of said element to an upper portion of said curved surface, whereby said element bears against said surface during pivotable movement of said arm.

2. A device as set forth in claim 1 wherein said flexible element is a generally flat, thin metal strip having one face thereof engageable with said curved surface.

3. A device as set forth in claim 1 wherein said linkage means includes a second arm adjacent to said first mentioned arm; said second arm being pivotally mounted adjacent an end opposite to the pivotal mounting of said first mentioned arm and movable in a vertical plane generally parallel to the plane of movement of said first I mentioned arm, said piston rod having an upwardly facing surface bearing against a downwardly facing surface of said second arm and said second arm carrying a lateral projection engaging a downwardly facing surface of said first mentioned arm. 

